Erosion is a natural process in which meteorological elements such as rain, wind, and snow remove soil, rock, and dissolved material from one location on the Earth's crust, and transport it to another location. While erosion may be a natural process, human activity has increased the rate of erosion in specific locations many times the rate at which erosion would occur in such areas naturally. For example, land surfaces adjacent man-made structures, such as the banks of canals, land adjacent roads, and artificially created drainage channels and other waterways are particularly susceptible to erosion because naturally occurring indigenous vegetation is removed in order to form the canal bank, road, or drainage channel.
The erosion resulting from the construction of such man-made structures can be mitigated by remediation of the land surfaces adjacent the canal, road, or waterway, such as by planting vegetation to replace the vegetation that was stripped away during their construction. However, there is a time interval between the planting of the replacement vegetation and the point at which the replacement vegetation is sufficiently developed to prevent further erosion of surface soil during which further erosion may occur.
Efforts have been made to retain the surface soil in place in these areas until such time as the replacement vegetation can mature to where the root structure of the replacement vegetation retains the surface soil in place. An example of such material is the flexible mat structure disclosed in U.S. Pat. No. 6,793,858 titled “Method and Apparatus for Forming a Flexible Mat Defined by Interconnected Concrete Panels,” the entire contents of which are incorporated herein by reference. That patent discloses a flexible mat structure in the form of spaced, interconnected concrete panels or blocks held together by an open mesh of a polymeric material such as a geogrid. The flexible mat structure is made by depositing concrete in the mold cavities of a rotating drum and embedding in the concrete material the open mesh geogrid. While the method is effective, there is a need to introduce additional efficiencies in the manufacture of such flexible mat structure. Further, there is a need to provide means to protect and promote the growth of the replacement vegetation beneath the erosion-prevention flexible mat structure. One particular need is to retain moisture beneath the flexible mat structure that will promote the growth of the replacement vegetation beneath the mat structure. Efforts have been made to place a second mat, made of wood shavings, beneath the flexible mat structure of tied concrete blocks. The second mat structure of wood shavings absorbs and retains moisture, thereby maintaining the surface soil beneath the mat in a moist condition that promotes the growth of replacement vegetation.
However, a disadvantage with that structure is that the wood shavings, an organic material, eventually decay and disintegrate, which may occur prior to the establishment of the replacement vegetation, during an interval when there is still a need for the moisture-retaining properties of the wood shavings. Further, as the wood shavings decay, they may break up to a size below which they together form the second mat that can be retained by the geogrid material of the tied concrete mat, and may be washed away by rain or blown away by wind. Accordingly, there is a need for an erosion-preventing laminate mat and installation system that maintains a moist surface soil condition for a longer period than prior structures.